i am seeing following error messages in database alert log. based on error message OS process was not able to connect one of the cell server. is there any way to find why it is failing to connect cell server?

The private network of your first exadata has a default range starting from 192.168.10.1 from the lowest compute node (db01).
A halfrack contains 11 components in the private network (4 nodes and 7 cells).
Hence 192.168.10.11 would be cell 7.
For a full rack this IP would match to cell 3.
Regards,
Tycho